Most snowmobiles have a frame made of bent sheet metal and metal tubing. A forward portion of the frame forms an engine cradle for supporting an internal combustion engine. A rearward portion of the frame forms a tunnel generally having an inverted U-shape. A drive track is disposed at least in part in the tunnel and is driven by the engine to propel the snowmobile. The combustion of fuel in the engine produces a significant amount of heat, and some of this heat is absorbed from the engine by a coolant, such as a mixture of water and ethylene glycol, to maintain the engine at a suitable temperature. The hot coolant is then pumped to a radiator, where the heat is dissipated to the atmosphere.
Referring to FIG. 1, during operation of a snowmobile, the rotation of the track 10 inside the tunnel 14 causes cold air and snow to circulate in the tunnel 14. It is common to mount one or more radiators 16, 20, 24 at one or more positions on the inside of the tunnel 14, facing the track 10, so that the circulation of cold air and snow can be used to dissipate heat from the coolant flowing through the radiators 16, 20, 24 to cool the engine. The number of radiators and their size and positions within the tunnel 14 are dictated by the cooling requirements of the engine. The radiator 16 is positioned on the front wall 18 of the tunnel 14, the radiator 20 is positioned on the top surface 22 of the tunnel 14, and the radiator 24 is positioned on the inside of a rear portion 26 of the tunnel 14 in combination with a snow flap 28 to increase the quantity of snow that comes into contact with the radiator 24.
Referring to FIG. 2, in an alternative embodiment the radiator 30 may be constructed as part of the top surface 32 of the tunnel 34, resulting in a reduced-weight snowmobile.
Although these arrangements provide adequate cooling for the engine of the snowmobile, they have a number of disadvantages.
When the radiator is positioned on the front wall of the tunnel, the metal frame conducts heat from the radiator to the engine compartment situated forwardly of the tunnel. As a result, the temperature of the engine compartment is increased, thereby reducing the effectiveness of the radiator to cool the engine.
Regardless of where the radiator is positioned on the tunnel, heat from the radiator is transferred to the tunnel. Snow coming into contact with the warm tunnel melts and later re-freezes, resulting in ice build-up on one or more of the tunnel, the track and the rear suspension assembly. The ice build-up increases the weight of the snowmobile. In addition, water that re-freezes on the track and rear suspension assembly when the snowmobile is not in use can in some cases result in the suspension or the track becoming jammed, making the snowmobile difficult to move.
In some snowmobiles, as described above, it is necessary to provide multiple radiators, to provide adequate cooling for the engine, resulting in increased weight of the snowmobile and increased cost of manufacture.
Therefore, there is a need for a snowmobile having a radiator arrangement that provides efficient cooling of the engine of the snowmobile.
There is also a need for a snowmobile having a radiator arrangement resulting in a lightweight cooling system.
There is also a need for a snowmobile having a radiator arrangement that reduces or eliminates the likelihood of ice build-up on the components of the snowmobile.